I rather like the idea of an illuminated gear knob actually, nice mod. Was it easy to fit?
From distant memory, this was what had to be done:
Pull out the existing ring & gaiter to expose the existing gearknob stem
There is a metal band holding the old gearknob to the stem - Hacksaw it off
Separate the ring from the old gaiter, but make a note of where the 'front' is first
Glue the new leather gaiter to the old ring, lining up carefully so that the front of the new gearknob lines up with the front of the ring
Wire in the gearknob to the illumination circuit (for example, hook off the ABS button's illumination wires)
Connect the new gearknob to the stem - ICT use a 3-way screw mechanism to clamp onto the flat face of the 'D' shaped stem.
Click the ring back into place, and now you are done.
It is entirely possible that I may have forgotten steps or details. There are a number of youtube videos showing the installation (although mostly in German), I would recommend watching them just to get a feel for the process even if you don't understand the language.
It was a bit more awkward than I described above, because for some reason the leather gaiter ICT supplied was a) slightly too short, maybe a few mm, leading to the problem I mentioned earlier, and b) was attached to the gearknob so that the 'front' was at about 10-o'clock instead of 12-o'clock, it had to be disassembled and moved around first. Must have been a friday-afternoon job, I wasn't impressed. But the end result looks nice.